1. Field of the Invention
The present invention is directed to a blowby injector and a blowby injection system, as well as a method for injecting internal combustion engine blowby flow into an exhaust gas flowstream.
2. Description of Related Art
In an internal combustion engine such as a diesel engine, the differential in pressure above and below the reciprocating pistons causes a small amount of gas to leak from the combustion chambers, past the pistons and the piston rings, and into the crankcase. Leakage gas flow into the crankcase can also result from the engine air handling system and/or on-engine air compressors. Such leakage flow is also commonly referred to as blowby. If a flow path is not provided for the blowby flow, pressure can build in the crankcase which can result in crankcase cover gasket leaks and shortened life of shaft seals.
The conventional prior art method for addressing the above noted problem is to vent the blowby flow to the environment via an open crankcase breather. The problem with such an approach is that the blowby flow picks up oil droplets as it passes through the crankcase, and releases them into the environment. This has a negative impact on the environment, and in some cases, does not satisfy environmental regulations.
One way to overcome the above-mentioned problems is to provide a closed circuit breather system in which the blowby flow is fed into the intake air of the engine for subsequent combustion. However, some of the oil carried with the blowby flow will cause carboning (also known as coking or carbonizing) upon contact with hot engine components such as turbocharger compressors and/or intake air intercoolers. Such carboning in the engine components can reduce the compression efficiency of the turbocharger compressor and/or reduce the effectiveness of the intercooler in removing heat from the charge air. To reduce this problem, gas/oil separators are often employed to try to minimize the flow of oil droplets into the intake air flow. However, provisions of such separators add cost to the engine, and in most cases, do not totally remove the oil content of the blowby flow. This limitation of gas/oil separators is due to the fact that the oil is generally in the form of a fine aerosol which can pass through such separators rather than in the form of sizeable droplets.
In an effort to overcome one or more of the above-mentioned problems, it has been proposed in patents GB 1531080 and DE 3312818, to feed the blowby flow into the exhaust system of the engine. One disadvantage of feeding the blowby flow into the exhaust before the muffler, or silencer as suggested in these references, is that the pressure in the exhaust system upstream of the muffler is likely to be significantly higher than the maximum pressure capability of the crankcase gasket and seals.
Japanese unexamined patent application 8-61037 proposes that the blowby flow be introduced into the exhaust system at a point downstream of the muffler. However, the apparatus disclosed in JP 8-61037 has one key disadvantage in that the blowby flow outlet protrudes into the hot exhaust gas flowstream. The blowby flow outlet is then heated by the hot exhaust. The temperature of the surfaces of the blowby outlet can exceed the boiling point of some of the lighter engine oil components. When the oil droplets then come into contact with the hot blowby outlet surface, the lighter oil components vaporize and leave a deposit of carbon behind. Over time, the carbon deposit accumulates and restricts the blowby flow which can lead to excessive crankcase pressure. Thus, frequent, and possibly difficult, decarboning of the blowby flow outlet is required to maintain proper operation of such an apparatus. Moreover, an apparatus constructed in accordance with JP 8-61037 where the blowby flow outlet is perpendicular to the wall of the tailpipe and formed with a bend, will exacerbate the carboning, and will be expensive to manufacture and install.
U.S. Pat. No. 6,418,712 to Darley discloses a blowby flow outlet that injects the blowby flow after the muffler of the exhaust system. The reference discloses that the blowby apparatus includes an adapter with a first hollow member that engages the wall of the exhaust system, and a nozzle with a second hollow member disposed within the first hollow member that serves as a blowby flow passage. The reference also discloses that the second hollow member is shorter than the first hollow member, and has an outer diameter smaller than the inner diameter of the first hollow member. Such dimensioning of the members is disclosed as defining a space between the members that provides an insulating effect to reduce the temperature of the blowby nozzle. The reference discloses that blowby nozzle temperatures as low as about 160° C. have been attained, thereby reducing the likelihood of carboning at the nozzle and associated service requirements.
However, when the blowby apparatus as described in the Darley reference is applied to high output internal combustion engines that tend to have higher exhaust gas temperatures, the temperature at the blowby nozzle has been found to be in the range of approximately 160° C. to 200° C. At these elevated temperatures, carboning can still occur from the oil mist in the blowby flow which can eventually lead to increased crankcase pressure and increased servicing requirements. Therefore, the above described problems regarding carboning of blowby devices remain unresolved by the prior art.
Therefore, there exists an unfulfilled need for a blowby system and method that can effectively maintain reduced crankcase pressure in an internal combustion engine. In addition, there exists an unfulfilled need for a blowby system and method that can minimize the likelihood of carboning so as to reduce service requirements. Finally, there exists an unfulfilled need for such a blowby system and method that may be used to minimize the likelihood of carboning, even when applied to high output engines that generate exhaust gas at elevated temperatures.